Transcription Factor Function in Chromatin

描述（由申请人提供）：为了理解正常的发育和分化，有必要确定细胞启动新的基因表达程序和促进特定细胞系形成的机制。通常，这涉及到转录沉默基因的激活，这些基因很可能与抑制性染色质结构结合在一起。有证据支持分化特异性转录调控因子和改造或改变染色质结构的酶协同作用，使基因组DNA更容易被转录机制所利用。SWI/SNF酶以ATP依赖的方式重塑核小体结构，并促进转录因子在体外和体内的功能。这些酶的组成部分是胚胎发育所必需的，有些还可以作为肿瘤抑制因子。此外，SWI/SNF酶与其他已知的肿瘤抑制因子相互作用，并参与细胞周期控制。因此，这些酶是正常细胞功能和分化发育所必需的，它们的失调与肿瘤的形成有关。骨骼肌分化一直是研究组织分化基本原理的模型。我们已经广泛使用细胞培养模型来鉴定和表征骨骼肌分化过程中染色质重塑酶的功能。通过对现有方法的修改，我们现在也能够检查染色质结构的变化和调节蛋白的相互作用，这些变化导致胚胎肌肉形成过程中的基因激活以及成人组织中基因表达的激活和维持。最近的进展使我们能够在胚胎肌肉形成开始时检查体中肌肉形成基因表达的调节，这进一步扩展了我们在胚胎发育背景下理解肌肉形成的分子控制的能力。这项更新应用将集中于SWI/SNF染色质重塑酶在几个水平上的功能。我们将研究SWI/SNF酶如何与肌源性转录因子和组蛋白修饰酶合作，促进肌源性基因表达的时间控制（AIm 1）。我们将研究肌生成所需的信号转导通路如何调节染色质重塑酶的功能（目的2）。最后，我们将研究SWI/SNF染色质重塑酶在细胞核中肌源性基因定位的分化依赖性重排中的功能，以及这一过程如何有助于肌源性基因表达的时间控制（目的3）。

DESCRIPTION (provided by applicant): To understand normal development and differentiation, it is necessary to determine the mechanisms by which cells initiate new programs of gene expression and promote formation of specific cell lineages. Typically, this involves activation of genes that are transcriptionally silent and that are likely incorporated into repressive chromatin structure. Evidence supports the idea that differentiation specific transcriptional regulators and enzymes that remodel or alter chromatin structure cooperate to render genomic DNA more accessible to the transcriptional machinery. SWI/SNF enzymes remodel nucleosome structure in an ATP dependent manner and facilitate transcription factor function in vitro and in vivo. Components of these enzymes are essential for embryonic development and some act as tumor suppressors. Additionally, SWI/SNF enzymes interact with other known tumor suppressors and are implicated in cell cycle control. Thus these enzymes are broadly required for normal cell function and for differentiation and development, and their misregulation is implicated in tumor formation. Skeletal muscle differentiation has long been a model for studying fundamental principles of tissue differentiation. We have made extensive use of cell culture models to identify and characterize chromatin remodeling enzyme function during skeletal muscle differentiation. Via modification of existing methodologies, we are now also capable of examining changes in chromatin structure and regulatory protein interactions that lead to gene activation during embryonic myogenesis and during the activation and maintenance of gene expression in adult tissue. Recent advances allow us to examine the regulation of myogenic gene expression specifically in the somites, at the start of myogenesis in the embryo, which further extends our abilities to understand the molecular control of myogenesis in the context of embryonic development. This renewal application will focus on SWI/SNF chromatin remodeling enzyme function at several levels. We will investigate how SWI/SNF enzymes cooperate with myogenic transcription factors and histone modifying enzymes to promote temporal control of myogenic gene expression (AIm 1). We will investigate how signal transduction pathways required for myogenesis regulate chromatin remodeling enzyme function (Aim 2). Finally, we will investigate SWI/SNF chromatin remodeling enzyme function in the differentiation dependent rearrangement of myogenic gene positioning in the nucleus and how this process contributes to the temporal control of myogenic gene expression (Aim 3).